The reaction of the CN radical with O-2 was studied using infrared diode laser absorption spectroscopy. Detection of NO and secondary N2O products was used to directly measure the product branching ratio. After consideration of possible secondary chemistry and comparison to kinetic modeling simulations, the branching ratio of the CN + O-2 reaction into the NO + CO channel was determined to be phi (NO + CO) = 0.20 +/- 0.02, with little or no temperature dependence over the range 296-475 K.